1. Field of the Invention
The present invention relates to a plasma processing method for processing a to-be-processed substrate such as a semiconductor substrate with the use of plasma, and a film forming method.
2. Description of the Related Art
In recent high-speed logic devices, reduction in dielectric constant (or obtaining Low-k) has been proceeded with, for the purpose of reducing interconnection capacitance. Further, study has been made for application of a porous material having large porosity for a very large-scale integrated circuit, and in particular, for a low dielectric constant film (i.e., a Low-k film) applied after a 65 nm technology node. Generally speaking, mechanical strength of such a porous Low-k film is low, and therefore, film peeling may occur, when copper is embedded and flattening is carried out in CMP after the Low-k film is produced. In order to avoid it, curing processing is previously required for the Low-k film, by thermal processing, UV processing, electron beam processing or such. Further, as plasma processing for such a Low-k film, a method of curing a Low-k film with the use of plasma of H2 gas is disclosed by, for example, Japanese Laid-open Patent Application No. 2003-503849.
When plasma curing processing is carried out with the use of H2 gas, a sequence of processing, such as that shown in FIG. 16, is carried out, for example.
First, after seasoning is carried not on the inside of a processing chamber (Step S301), a to-be-processed substrate is brought in the processing chamber (Step S302). Next, an Ar gas is introduced in the processing chamber for the purpose of stabilizing plasma, it is heated, and a pressure there is adjusted (Step S303). Then, plasma ignition is carried out, and thus, Ar plasma is generated (Step S304). After the plasma ignition, a flow rate of the Ar gas is controlled (Step S305), and the thus-generated Ar gas plasma is sufficiently stabilized. After that, an H2 gas is introduced, and curing processing is started (Step S306). After the curing is completed, plasma is stopped, and predetermined end processing, such as exhaust processing and so forth, is carried out.
When curing processing of a Low-k film is carried out by the above-mentioned thermal processing, UV processing or electronic beam processing, degradation in the Low-k film may occur, such as an increase in a film shrinkage factor or such.
Further, when plasma processing is carried out on a Low-k film in a method such as that described above with reference to FIG. 16, a cured film is produced only in the vicinity of a surface of the Low-k film, and curing may not be carried out inside deeply. Thereby, in etching processing carried out after that for example, an etching rate may differ much between the vicinity of the surface and the inside of the Low-k film. Thus, proper control of an etched shape may become difficult. Furthermore, when only the vicinity of the surface of the film is cured, the original purpose of curing processing cannot be sufficiently achieved accordingly, a mechanical strength of the Low-k film may not be sufficiently increased, a wall part configuring a wiring pattern may fall down, and thus, a subsequent process may not be carried out. Further, since wetting property (adherence) may not be sufficient, and thus film peeling may occur, so that leakage electric current may increase.